In recent years, as one of the causes of the global warming phenomenon, the greenhouse effect caused by CO2 has been pointed out, and countermeasures thereagainst have also been a pressing need internationally in order to protect the environment of earth. As generation sources of CO2, in the fields of activity of all human beings which combust fossil fuels, the need for suppression of emission of CO2 tends to become stronger. Along with this, methods of bringing combusted exhaust gas of boilers into contact with an amine-based CO2 absorption liquid and eliminating and recovering CO2 in the combusted exhaust gas, and methods of storing the recovered CO2 without being emitted to atmospheric air have been energetically studied for, for example, power generation facilities, such as thermoelectric power plants that use a large quantity of fossil fuels.
Additionally, as a method of removing and recovering CO2 from a combustion exhaust gas, using the CO2 absorption liquid as above, there is adopted a method including a step of bringing the combustion exhaust gas into contact with the CO2 absorption liquid in an absorption tower; and a step of heating an absorption liquid which has absorbed CO2 in a regeneration tower, separating CO2, and regenerating the CO2 absorption liquid, and circulating the regenerated CO2 absorption liquid again to the absorption tower and reusing the regenerated CO2 absorption liquid (PTL 1).
Meanwhile, in CO2 recovery devices, it is necessary to reduce the consumption amount of steam for regeneration of an absorption liquid, and achieve further energy saving. Additionally, in a case where solid contents, such as dust in exhaust gas, are accumulated in the absorption liquid, when the solid contents are separated and removed from the absorption liquid, reducing the amount of loss of the absorption liquid adhering to discharged solid contents and efficiently removing the solid contents from the absorption liquid are challenges.
For this reason, the related art suggests carrying out normal cleaning of a filter using water containing a low-concentration CO2 absorption liquid, thereby removing the solid contents (PTL 2).